Analysis of Floral Homeotic Regulatory Gene Function in the Angiosperms

基于许多花同源基因在序列和功能上的相似性，有人提出控制花发育的分子机制在菊科植物中是相似的，也许在所有被子植物物种中都是相似的。尽管如此，花表现出显著的形态多样性，而且人们认为特定的花器官类型可能进化了不止一次。特别是，花瓣被认为在被子植物中出现过无数次。这些花瓣的独立起源表明，在不同的物种中，确定花瓣同一性的分子机制可能是不同的。本研究旨在明确验证aptala3 （AP3）和PISTILLATA （PI）基因的表达和功能在其他被子植物分支中可能具有不同的作用，这两个基因已知在高等植物物种中控制花瓣的特性。提出了三组实验来开始了解AP3和PI同源基因的功能如何在进化时间中被调节。首先，我们将对AP3和PI同源基因在被子植物中进行表达分析，看看它们的表达变化是否与花瓣的独立起源有关。其次，最近的工作已经确定了另一个基因TM6，它似乎是AP3的类似物，也可能在花瓣发育中起作用。矮牵牛和烟草TM6同源植物的功能缺失表型将被产生和表征，以确定tmd样基因的作用。第三，最近的系统发育分析已经确定了保守的a.p p3和PI羧基末端基序；我们将在转基因拟南芥中进行缺失和交换实验，以确定这些保守序列的作用。

Based on the similarities in sequence and function of a number of floral homeotic genes, it has been proposed that the molecular mechanisms controlling floral development are similar across dicots, and perhaps across all angiosperm species. Nonetheless, flowers display remarkable morphological diversity, and it is thought that particular floral organ types may have evolved more than once. In particular, petals are thought to have arisen numerous times in the angiosperms. These independent origins of petals imply that the molecular mechanisms specifying petal identity may be different in different species. This proposal seeks to explicitly test the hypothesis that the expression and function of the APETALA3 (AP3) and PISTILLATA (PI) genes which are known to control petal identity in higher eudicot species may have different roles in other angiosperm clades. Three sets of experiments are proposed to begin to understand how the functions of AP3 and PI orthologous genes may have been modulated over evolutionary time. First, expression analyses of AP3 and PI orthologs will be carried out in selected angiosperm species to see if changes in their expression correlate with the independent origins of petals. Second, recent work has identified another gene, TM6, which appears to be an AP3 paralog and may also function in petal development. Loss-of-function phenotypes in TM6 orthologs in Petunia and Nicotiana will be generated and characterized to determine the role of TMd-like genes. Third, recent phylogenetic analyses have identified conserved A.P3 and PI carboxy-terminal motifs; deletion and swapping experiments will be carried out in transgenic Arabidopsis to determine the role(s) of these conserved sequences.